Fuel additive

ABSTRACT

A composition for use as a fuel additive for a hydrocarbon fuel. The additive is in the form of particles of one or more complex oxides having a nominal composition as set out in formula (1): 
         A   x   B   1−y   M   y O n    (1)
 
     Wherein A is selected from one or more group III elements including the lanthanide elements or one or more divalent or monovalent cations; B is selected from one or more elements with atomic number 22 to 24, 40 to 42 and 72 to 75; M is selected from one or more elements with atomic number 25 to 30; x is defined as a number where 0&lt;x&lt;1 ; and y is defined as a number where 0&lt;y&lt;0.5.

FIELD OF THE INVENTION

The present invention relates to a fuel additive. In a more specificembodiment, the present invention relates to a fuel additive that iseffective even with high sulphur content in the fuel.

BACKGROUND TO THE INVENTION

Cerium oxide has been extensively used as a component in the catalyst ofthree-way converters for the elimination of toxic exhaust emissions inautomobiles. The cerium oxide contained within the catalyst can act as achemically active component, working as an oxygen store by the releaseof oxygen in the presence of reductive gases, and removal of oxygen byinteraction with oxidised species. Cerium oxide may store and releaseoxygen by the following processes:

2CeO_(2<=>Ce) ₂O₃+0.5 O₂

Cerium oxide has also been used as an additive to be added to fuels. Insuch uses, the cerium oxide provides a catalytic effect that has beenfound to reduce the emission of toxic exhaust gases. Addition of ceriumoxide has also been found to improve the combustion of the fuel as itpasses through an internal combustion engine. Due to improvedcombustion, far less pollutants are formed. For example, when ceriumoxide is used as a fuel additive for diesel engines, an increase inefficiency of approx 10% has been achieved and a reduction in emissionsof NOx gases of up to 65% has also been measured [ref Oxonica Website].

In order to keep the cerium oxide particles suspended in the fuel, it isusually necessary to prepare a colloidal dispersion of the cerium oxideparticles which requires the cerium oxide particles to be very fine, forexample, sub-micron particles having a maximum particle size of up to300 nm.

There have been several documents described in the patent literaturethat discuss the use of cerium oxide, or modified forms of cerium oxide,as fuel additives.

WO 03/040270 (the entire contents of which are herein incorporated bycross reference) describes a fuel additive which comprises a particle ofcerium oxide which has been doped with a divalent or trivalent metal ormetalloid which is a rare earth metal, a transition metal, including anoble metal, or a metal of groups IIA, IIIB, VB, or VIB of the periodictable, and a polar or non-polar organic solvent.

The doped cerium oxide particle described in this patent application mayhave the following formula:

Ce_(1−x)M_(x)O₂,

where M is the metal or metalloid as described above, particularly Rh,Cu, Ag, Au, Pd, Pt, Sb, Se, Fe, Ga, Mg, Mn, Cr, Be, B, Co, V and Ca aswell as Pr, Sm, and Gd and x has a value of up to 0.3. Copper isparticularly preferred.

Alternatively, the doped cerium oxide particle may have followingformula:

[(CeO₂)_(1−n)(REO_(y))_(n)]_(1−k)M′_(k)

where M′ is said metal or metalloid other than a rare earth, RE is arare earth, y is one or 1.5 and each of n and k has a value up to 0.5,preferably up to 0.3.

Copper is the preferred metal or metalloid.

WO 2004/065529 (the entire contents of which are herein incorporated bycross reference) has a similar disclosure, but it relates to a method ofimproving the efficiency of a fuel for an internal combustion enginewhich comprises adding to the fuel prior to the introduction of the fuelto a vehicle or other apparatus comprising an internal combustionengine, cerium oxide and/or doped cerium oxide and, optionally, one ormore fuel additives.

The doped cerium oxides that may be used in the invention described inthis patent application will have the formula Ce_(1−x)M_(x)O₂, where Mis the metal or metalloid as described above, particularly Rh, Cu, Ag,Au, Pd, Pt, Sb, Se, Fe, Ti, Ga, Mg, Mn, Cr, Be, B, Co, V and Ca as wellas Pr, Sm, and Gd.

The fuel additive may be provided in the form of a product to be mixedwith the fuel at the point of dispensing the fuel (for example, at aservice station). In these embodiments, the fuel additive may be poureddirectly into the fuel tank of a motor vehicle prior to or just afterfilling up the fuel tank of the motor vehicle. Alternatively, the fueladditive may be mixed with the fuel in the fuel storage tanks at theservice station. However, it is even more desirable to have the fueladditive mixed with the fuel at the point of production of the fuel,which is typically at an oil refinery.

In our copending international patent application number PCT/AU2007/000488, the entire contents of which are herein incorporated bycross reference, we describe a material that is useful as an exhaustemissions catalyst.

The present applicant does not concede that the prior art discussed herein forms part of the common general knowledge in Australia or elsewhere.

Throughout this specification, the word “comprising” and its grammaticalequivalents shall be taken to have an inclusive meaning unless thecontext of use clearly indicates otherwise.

BRIEF DESCRIPTION OF THE INVENTION

The present inventors have now discovered that the catalytic materialdescribed in our copending international patent application numberPCT/AU 2007/000488 is also especially useful as a fuel additive.

In a first aspect, the present invention provides a fuel additivecomprising one or more complex oxides having a nominal composition asset out in formula (1):

A _(x) B _(1−y) M _(y)O_(n)   (1)

wherein

A is selected from one or more group III elements including thelanthanide elements or one or more divalent or monovalent cations;

B is selected from one or more elements with atomic number 22 to 24, 40to 42 and 72 to 75;

M is selected from one or more elements with atomic number 25 to 30;

x is defined as a number where 0<x≦1;

y is defined as a number where 0≦y<0.5.

In one embodiment, the one or more complex oxides have a generalcomposition as set out in formula (2):

A _(x) A′ _(w) B _(1−y) M _(y)O_(n)   (2)

wherein

A is one or more group III elements including the lanthanide elements;

A′ is one or more divalent or monovalent cations;

w is defined as a number where 0≦w≦1;

0.5<x+w<1 and

B, M, P, x and y are as set out in formula (1).

In a preferred embodiment A is selected from La, Ce, Sm and Nd, A′ isselected from Sr, Ba, and Ca, B is selected from Ti, V, W and Mo, and Mis selected from Cu and Ni.

In a more preferred embodiment A is La and/or Ce, A′ is Sr, B is Ti, andM is Cu and/or Ni. In this embodiment, the complex oxide has the generalformula as set out in formula (3):

(La,Ce)_(x)Sr_(w)Ti_(1−y)M_(y)O_(n)   (3)

In a further preferred embodiment at least one of the complex oxidephases is a perovskite with a general formula (4):

A _(x)A′_(w)B_(1−y)M_(y)O₃   (4)

and more preferably of formula (5):

(La,Ce)_(x)Sr_(w)Ti_(1−y)M_(y)O₃   (5)

where the terms in (4) and (5) are as defined in (1) and (2) above.

The perovskite component of the formula may suitably exhibitsubstantially homogenous and phase-pure composition.

The complex oxide material may have an initial surface area greater thanapproximately 15 m²/g, preferably greater than approximately 20 m²/g,more preferably greater than approximately 30 m²/g, and a surface areaafter aging for 2 hours at 1000° C. in air greater than approximately 5m²/g, preferably greater than approximately 10 m²/g, more preferablygreater than approximately 15 m²/g.

The complex oxide material may generally exhibit an average grain sizeof approximately 2 nm to approximately 150 nm, preferably approximately2 to 100 nm and has pores ranging in size from approximately 7 nm toapproximately 250 nm, more preferably approximately 10 nm toapproximately 150 nm. However, the average grain and pore size of thecomplex oxide materials may vary, depending on the specific complexoxide selected.

More preferably, the complex oxide material may exhibit a substantiallydisperse pore size range.

The complex oxide material of the invention may be formed by mixingprecursors of the elements described above in the general formula (1)followed by appropriate heat treatment to form the target phases. Theprecursors may be of any suitable form such as salts, oxides or metalsof the elements used. The precursor mixture may be in the form of amixture of solids, a solution or a combination of solids and solutions.The solutions may be formed by dissolving salts in a solvent such aswater, acid, alkali or alcohols. The salts may be but are not limited tonitrates, carbonates, oxides, acetates, oxalates, and chlorides.Organometallic form of elements such as alkoxides may also be used.

Solid dispersions may also be used as suitable precursor materials.

Various methods of mixing precursors to produce the complex oxide mayinclude but are not limited to techniques such as, mixing and grinding,co-precipitation, thermal evaporation and spray pyrolysis, polymer andsurfactant complex mixing and sol gel. Where necessary, the final phasecomposition is achieved by thermal processing following mixing. Theheating step may be carried out using any suitable heating apparatus andmay include but are not limited to, hot plates or other heatedsubstrates such as used in spray pyrolysis, ovens stationary tablefurnaces, rotary furnaces, induction furnaces, fluid bed furnace, bathfurnace, flash furnace, vacuum furnace, rotary dryers, spray dryers,spin-flash dryers.

In a preferred embodiment a homogeneous complex oxide is formed by themethod outlined in U.S. Pat. No. 6,752,679, “Production of Fine-GrainedParticles”, the entire contents of which are herein incorporated bycross reference.

In a further preferred embodiment a homogeneous complex oxide is formed,has nano-sized grains in the size range indicated and nano-scale poresin the size range indicated by using the method outlined in U.S. Pat.No. 6,752,679 and U.S. Patent application 60/538867, the entire contentsof which are herein incorporated by cross reference.

In a more preferred embodiment a homogeneous complex oxide is formed,has nano-sized grains in the size range indicated and nano-scale poresin the size range indicated and uses an aqueous colloidal dispersion ofnano-scale particles as one of the precursor elements by using themethod outlined in U.S. Pat. No. 6,752,679 and U.S. Patent application60/538867 and U.S. patent application 60/582905, the entire contents ofwhich are herein incorporated by cross reference.

In some embodiments, the complex oxide is provided in the form ofdispersed particles. The dispersed particles may have a particle size ofup to 300 nm. The dispersed particles may be formed by forming thecomplex oxide material in accordance with the methods as described inU.S. Pat. No. 6,752,679 or U.S. Patent application 60/538867 or U.S.patent application 60/582905 and subsequently grinding the complex oxidematerial to form dispersed particles. It has been surprisingly foundthat the agglomerated particles that are formed by the methods describedin our U.S. Pat. No. 6,752,679 and U.S. Patent application 60/538867 andU.S. patent application 60/582905 are only loosely agglomerated and canbe easily ground or milled to form dispersed particles.

In some embodiments of the present invention, A is Ce, B is Ti, y iszero, z is zero and n is 4. This results in a complex oxide having theformula CeTiO₄.

The fuel additive in accordance with the present invention may furthercomprise one or more solvents. The one or more solvents may comprise anorganic solvent. The one or more solvents may comprise a non-polarorganic solvent or a polar organic solvent. The person skilled in theart will readily understand that a number of solvents may be used in thefuel additive in accordance with the present invention. The solvents aresoluble in the fuel and act as a carrier or delivery agent for theparticles of metal oxide.

A number of other components may also be added to the fuel additive.These other components may include:

-   -   Detergents,    -   dehazers    -   anti-foaming agents    -   ignition improvers    -   anti-rust agents or corrosion inhibitors    -   deodorants    -   antioxidants    -   metal deactivatorss    -   lubricating agents    -   dyes.

The skilled person will readily understand the nature and sources ofsupply of the above additives. The skilled person will also understandhow much of each additive may be added to the fuel additive.

The present inventors have found that complex metal oxides, as describedwith reference to the first aspect of the present invention, areparticularly suitable for use as fuel additives in accordance with thepresent invention. In particular, the fuel additives of the presentinvention show enhanced resistance to deactivation or poisoning bysulphur. The present inventors believe that, due to the enhancedresistance to deactivation or poisoning by sulphur, the fuel additive inaccordance with the present invention is particularly suitable foradding to fuels, such as diesel fuel, at the manufacturing facility ofthe fuels (which will typically be an oil refinery) or at bulk storagefacilities for the fuel. Previous efforts to incorporate ceriumoxide-based fuel additives into fuels at an oil refinery or bulk storagefacilities have resulted in inadequate performance of the fuel additive,which the present inventors have postulated is due to deactivation orpoisoning by sulphur. In this regard, it will be understood that evenmodern high quality diesel fuels contain up to 50 ppm sulphur.

In a second aspect, the present invention provides a method for making afuel additive comprising the steps of forming a complex metal oxide offormula (1) as described above, the complex metal oxide being formed inthe form of the agglomerated particles having nano sized grains,breaking the agglomerates of particles to form dispersed particles ofcomplex metal oxide having a particle size of less than 300 nm andadding said particles to a fuel.

In some embodiments, the method may further comprise the step of mixingthe particles with one or more solvents. The solvent(s) are soluble inthe fuel and act as a carrier or delivery agent for the particles ofmetal oxide. Other additives, as described above, may also be added tothe fuel additive.

In a third aspect, the present invention provides a fuel additivecomprising a solvent and one or more complex oxides having a nominalcomposition as set out in formula (1) above. The solvent(s) are solublein the fuel and act as a carrier or delivery agent for the particles ofmetal oxide. The fuel additive may be in the form of a suspension or adispersion of particles of the complex oxide in the solvent.

In a further aspect, the present invention also provides a fuelcomprising a hydrocarbon-based fuel and a fuel additive as describedherein. The hydrocarbon-based fuel may be diesel fuel.

As will be understood by the person skilled in the art, in all of thechemical formulae given in this specification, n will be a value thatessentially balances the oxygen with the metallic species in theformulae.

EXAMPLES Material Preparation Example 1

A complex metal oxide of the nominal formula La_(0.8)Sr_(0.2)TiO₃ plus10 w % CeO₂ was produced as follows.

A solution containing all the required elements except Ti was made bymixing 45 mls of water, 10 g of nitric acid, 46.29 g of lanthanumnitrate hexahydrate, 5.66 g of strontium nitrate and 7.57 g of ceriumnitrate hexahydrate.

10.67 g of Titanium-based nano-particles were added to the solution andstirred at a temperature of 50° C. until the particles were dispersedand a clear solution was formed.

The solution was then added to 16 g of carbon black and mixed with ahigh-speed stirrer. The resulting mixture was added to 70 g of anionicsurfactant and again mixed with a high-speed stirrer.

The final mixture was heat treated slowly to 650° C. and then treated at800° C. for 2 hrs and a further 2 hrs at 1000° C. XRD analysis showedthat the perovskite phase LaSr₀₅Ti₂O₆ and (Ce,La)₂Ti₂O₇ were the maintypes of phases present in Example 1.

Example 2

A complex metal oxide of nominal formulaLa_(0.5)Sr_(0.25)Ti_(0.96)Ni_(0.04) 0 _(n) plus 10 w % CeO₂ was producedusing a similar method to Example 1. XRD analysis showed that theperovskite phase LaSr_(0.5)Ti₂O₆ and (Ce,La)₂Ti₂O₇ were the main typesof phases present.

Example 3

A complex metal oxide of nominal formulaLa_(0.8)Sr_(0.2)Ti_(0.96)Ni_(0.04)O_(n) plus 10 w % CeO₂ was producedusing a similar method to Example 1. XRD analysis showed that theperovskite phase LaSr_(0.5)Ti₂O₆ and (Ce,La)₂Ti₂O₇ were the main typesof phases present.

Example 4

A complex metal oxide of nominal formulaLa_(0.8)Sr_(0.2)Ti_(0.93)Ni_(0.04)Cu_(0.03)O_(n) plus 10 w % CeO₂ wasproduced using a similar method to Example 1. XRD analysis showed thatthe perovskite phase LaSr_(0.5)Ti₂O₆ and (Ce,La)₂Ti₂O₇ were the maintypes of phases present.

Example 5

A complex metal oxide of nominal formula LaTi_(0.96)Ni_(0.04)O_(n) plus10 w % CeO₂ was produced using a similar method to Example 1. XRDanalysis showed that the perovskite phase LaSr_(0.5)Ti₂O₆ and(Ce,La)₂Ti₂O₇ were the main types of phases present.

Example 6

A complex metal oxide of nominal formula CeTi_(0.96)Ni_(0.04)O_(n) wasproduced using a similar method to Example 1. XRD analysis showed thatthe (Ce,La)₂Ti₂O₇ phase was the main type of phase present.

1-18. (canceled)
 19. A composition for use as a fuel additive comprisingparticles of one or more complex oxides having a nominal composition asset out in formula (1):A_(x)B_(1−y)M_(y)O_(n)   (1) wherein A is selected from one or moregroup III elements including the lanthanide elements or one or moredivalent or monovalent cations; B is selected from one or more elementswith atomic number 22 to 24, 40 to 42 and 72 to 75; M is selected fromone or more elements with atomic number 25 to 30; x is defined as anumber where 0<x<1; and y is defined as a number where 0<y<0.5.
 20. Acomposition for use as a fuel additive as claimed in claim 19, whereinthe one or more complex oxides have a nominal composition as set out informula (2):A_(x)A′_(w)B_(1−y)M_(y)O_(n)   (2) wherein A is one or more group IIIelements including the lanthanide elements; A′ is one or more divalentor monovalent cations; w is defined as a number where 0≦w≦1; and0.5<x+w<1.
 21. A composition for use as a fuel additive as claimed inclaim 20 wherein A is selected from La, Ce, Sm and Nd, A′ is selectedfrom Sr, Ba, and Ca, B is selected from Ti, V, W and Mo, and M isselected from Cu and Ni.
 22. A composition for use as a fuel additive asclaimed in claim 21 wherein A is La or Ce, A′ is Sr, B is Ti, and M isCu or Ni and the complex oxide has the general formula as set out informula (3):(La,Ce)_(x)Sr_(w)Ti_(1−y)M_(y)O_(n)   (3).
 23. A composition for use asa fuel additive as claimed in claim 20 wherein at least one complexoxide phase is a perovskite with a general formula (4):A_(x)A′_(w)B_(1−y)M_(y)O₃   (4).
 24. A composition for use as a fueladditive as claimed in claim 23 wherein at least one complex oxide phaseis a perovskite with a general formula (5):(La,Ce)_(x)Sr_(w)Ti_(1−y)M_(y)O₃   (5).
 25. A composition for use as afuel additive as claimed in claim 19 wherein the complex oxide materialhas an initial surface area greater than approximately 15 m²/g, and asurface area after aging for 2 hours at 1000° C. in air greater thanapproximately 5 m²/g.
 26. A composition for use as a fuel additive asclaimed in claim 25 wherein the complex oxide material has an initialsurface area greater than approximately 30 m²/g, and a surface areaafter aging for 2 hours at 1000° C. in air greater than approximately 15m²/g.
 27. A composition for use as a fuel additive as claimed in claim19 wherein the complex oxide material exhibits an average grain size ofapproximately 2 nm to approximately 150 nm and has pores ranging in sizefrom approximately 7 nm to approximately 250 nm.
 28. A composition foruse as a fuel additive as claimed in any one of the preceding claimswherein A is Ce, B is Ti, y is zero, and n is 4 and the complex oxidehas the formula CeTiO₄.
 29. A composition comprising a fuel and the fueladditive of claim
 19. 30. A composition as claimed in claim 29 whereinthe fuel comprises a hydrocarbon-based fuel.
 31. A composition asclaimed in claim 29 wherein the fuel is a diesel fuel.
 32. A compositionas claimed in claim 29 further comprising one or more solvents that aresoluble in the fuel and that form a suspension or dispersion of theoxide particles in the solvent which then acts as a carrier or deliveryagent for the fuel additive.
 33. A composition as claimed in claim 29further comprising other components or additives selected from the groupcomprising detergents, dehazers, anti-foaming agents, ignitionimprovers, anti-rust agents or corrosion inhibitors, deodorants,antioxidants, metal deactivators, lubricating agents, dyes or mixturesof two or more thereof.
 34. A method for making a fuel additivecomprising one or more complex oxides having a nominal composition asset out in formula (1):A _(x)B_(1−y)M_(y)O_(n)   (1) wherein A is selected from one or moregroup III elements including the lanthanide elements or one or moredivalent or monovalent cations; B is selected from one or more elementswith atomic number 22 to 24, 40 to 42 and 72 to 75; M is selected fromone or more elements with atomic number 25 to 30; x is defined as anumber where 0<x<1; and y is defined as a number where 0<y<0.5, whichmethod comprises: forming a complex metal oxide of formula (1), thecomplex metal oxide being formed in the form of the agglomeratedparticles having nano sized grains; breaking the agglomerates ofparticles to form dispersed particles of complex metal oxide having aparticle size of less than 300 nm; and adding the particles to a fuel.35. A method as claimed in claim 34 which further comprises mixing theparticles with one or more solvents that are soluble in the fuel andthat form a suspension or dispersion of the oxide particles in thesolvent which then acts as a carrier or delivery agent for the fueladditive.
 36. A method as claimed in claim 35 wherein the fuel comprisesa hydrocarbon-based fuel.
 37. A method as claimed in claim 35 whereinthe fuel is a diesel fuel.
 38. A method for making a fuel comprisingrefining oil at a refinery to form a fuel and adding a composition foruse as a fuel additive as claimed in of claim 19 to the fuel at therefinery or at a bulk storage facility for the fuel.
 39. A method asclaimed in claim 39 wherein the fuel comprises a hydrocarbon-based fuel.40. A method as claimed in claim 40 wherein the fuel is a diesel fuel.